Field of the Invention
The present invention relates to load balancer devices and structure for controlling the operation of a plurality of servers. This invention further relates generally to data communications, and more specifically, to systems and methods to dynamically load balance servers.
Description of the Related Art
Network traffic densities are increasing constantly. The adoption of Software Defined Network (SDN) technology is on the rise for the powerful control it offers over network infrastructure. It is a matter of time before it becomes a part of mainstream adoption. There will be a transitional period in which elements of SDN are used alongside traditional networking technologies and newer overlay solutions. As SDN adoption continues, load balancers will play a critical role in providing the required intelligence for flexible and increasingly effective network deployments.
More specifically, load balancing is a process of allocating a plurality of client sessions among a plurality of server resources. The goals of load balancing will typically include some combination of maximizing throughput, improving resource utilization, and minimizing average response time. In addition, the ability to load balance among multiple servers will increase reliability through redundancy. If one or more servers should prove unreliable, load balancing can direct client sessions to other remaining reliable servers. Load balancing is commonly used to distribute tasks across a pool of web servers according to various scheduling algorithms. An apparatus that performs the load balancing according to a scheduling algorithm is referred to as a “load balancer.”
One such scheduling algorithm used by a load balancer for apportioning work among a pool of web servers is round-robin scheduling. In round-robin scheduling, sessions are distributed in equal number to each web server in circular order. Although round-robin scheduling equalizes the number of requests sent to each web server, congestion in the underlying data network connections to each of the servers can vary, resulting in unpredictable delays in response time. Thus, although the number of provided requests is equalized among the web servers, the costs are not equally distributed. Consequently, even though each of the web servers is allocated the same number of requests, the work queue for some web servers may grow long while other web servers may have few requests in their respective queues. Because response time is roughly proportional to the number of requests in a queue, the average response time will suffer when the number of queued requests becomes unequally distributed among web servers.
In traditional networks there is no end-to-end visibility of network paths, and application traffic is not always routed optimally. More specifically, in conventional networks with load balanced servers, including those that are software defined and controlled by an SDN (software defined network) controller, the load balancer looks at the data traffic congestion at the servers and does not take into account the congestion through the network itself. For example, a path through the network, or a network egress port to which a server is connected, may be overloaded with client requests and server responses thereto. The round robin sequencing, or even a weighted round robin sequencing which is based in part on the data traffic capabilities of the individual servers, performed by conventional load balancers, do not factor in the response times or propagation delays through the network or data velocity at the network egress ports.
An SDN controller generates statistical information from which such data traffic congestion through the network may be derived. However, heretofore, no conventional load balancer taps this statistical information from the SDN controller to provide adaptive load balancing which dynamically adjusts to changing data traffic congestion through the network for intelligent data traffic steering.